Suchergebnisse

Role Plays and Creative Activities: Teaching Social Skills and Self-Understanding presents over 150 role plays, micro role plays (role plays that run for a few minutes), creative activities, and guided imagery (stories with psychological content to be read to the children) which Dr. Christopher Glenn has developed and used for over thirty years.

Glass-ceramic materials with composition 0.9Nd3+–80SiO2–20LaF3 were successfully obtained and further heat-treated at 450 °C for 6 h. Stable and homogeneous LaF3 nanoparticle suspensions with and without Nd3+ were first prepared by a chemical route, incorporating polyvinylpyrrolidone (PVP) as dispersant. The suspensions were then concentrated and characterised by XRD, HRTEM and zeta potential, confirming that LaF3 crystallises as the only phase, with particle size around 16 nm. The suspensions were incorporated in a silica sol to obtain a 0.9Nd3+–20LaF3–80SiO2 particulate sol, xerogel and glass-ceramic. HRTEM confirmed the homogeneous incorporation of the doped nanocrystals into the SiO2 matrix without modification of the nanoparticle structure. Rietveld refinement was used to determine the crystallinity and quantity of LaF3 nanoparticles present in the glass-ceramic after treatment of the particulate sol at 450 °C for 6 h. Luminescence measurements of near infrared Nd3+ ion emissions in the lanthanum fluoride nanoparticles and SiO2–LaF3 glass-ceramic showed well-structured emission spectra with lifetimes similar to those of theoretical Nd+3 in LaF3 crystals. ; The authors acknowledge the financial support from MINECO under projects MAT2017-87035-C2-1-P/-2-P (AEI/FEDER, UE), Basque Country University GIU17/014 and Basque Government PIBA2018-24. This article is a part of the dissemination activities of the project FunGlass, which has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 739566. The authors also acknowledge the support of the Transmission Electron Microscope (TEM) service of the Institute of Catalysis and Petrochemistry (CSIC). ; Peer reviewed

This article belongs to the Special Issue Glass-Ceramics: Improving Glass Properties through Crystallization. ; In this study, transparent oxyfluoride glass-ceramics (GCs) with NaLaF4 nanocrystals (NCs) were prepared by the sol–gel method for the first time. Three different molar ratios of La(CH3COO)3/Na(CH3COO) were used to obtain the GCs, which were sintered at 450, 550 and 650 °C for 1 min. X-ray diffraction (XRD) was employed to follow the evolution of the xerogel during the heat treatments and to study crystal growth for the three temperatures. In all cases, the LaF3 crystalline phase was present, but crystallization of NaLaF4 was only promoted at 650 °C. Thermogravimetric and thermodifferential analysis (TGA-DTA) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the crystallization process. High-resolution transmission electron microscopy (HRTEM) was employed to confirm NaLaF4 crystallization and determine the size distribution. The incorporation of Nd3+ ion into NaLaF4 and LaF3 nanocrystals was confirmed by site-selective emission and excitation spectra. The Nd3+ emission intensities in both phases depend not only on the NaLaF4/LaF3 ratio but also on their emission efficiencies. ; The authors acknowledge financial support from MINECO under projects MAT2017-87035-C2-1-P/-2-P (AEI/FEDER, UE), and Basque Government PIBA2018-24. This article is a part of the dissemination activities of the project FunGlass, which has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 739566. ; Peer reviewed

[EN] The BaZrCeYO-BaPrO perovskite system, of interest for high-temperature electrochemical applications involving mixed protonic-electronic conductivity, forms a solid-solution with a wide interval of Ba substoichiometry in the range Ba(CeZr)PrYO, 0 ≤ x ≤ 1. Structural phase transitions mapped as a function of temperature and composition by high-resolution neutron powder diffraction and synchrotron X-ray diffraction reveal higher symmetry for lower Pr content and higher temperatures, with the largest stability field observed for rhombohedral symmetry (space group, R3c). Rietveld refinement, supported by magnetic-susceptibility measurements, indicates that partitioning of the B-site cations over the A and B perovskite sites compensates Ba substoichiometry in preference to A-site vacancy formation and that multiple cations are distributed over both sites. Electron-hole transport dominates electrical conductivity in both wet and dry oxidizing conditions, with total conductivity reaching a value of 0.5 S cm for the x = 1 end-member in dry air at 1173 K. Higher electrical conductivity and the displacement of oxygen loss to higher temperatures with increasing Pr content both reflect the role of Pr in promoting hole formation at the expense of oxygen vacancies. In more reducing conditions (N) and at low Pr contents, conductivity is higher in humidified atmospheres (0.023 atm pHO) indicating a protonic contribution to transport, whereas the greater electron-hole conductivity with increasing Pr content results in lower conductivity in humidified N due to the creation of protonic defects and the consumption of holes. ; We thank the MINECO, Spain (ENE2015-66183-R and MAT2016-78362-C4-1-R), CSIC, Spain (i-link0743), and CAPES, Brazil (PVE, Proceso 88881.03418/2013-1). Access to the neutron facilities at the Institut Laue Langevin (Grenoble, France) and the National Synchrotron Light Laboratory (LNLS, Campinas, Brazil) under grant 5-24-55(D2B) and research proposal D10B-XRD1-16166, respectively, is gratefully acknowledged. We also thank the FCT, PTDC/CTM-EME/6319/2014, QREN, FEDER, and COMPETE Portugal and the European Social Fund, European Union. U.A. acknowledges the Universidad San Pablo for financial support. We would also like to thank Steven Kermorvant and Alexandre Bosser of the IUT, University of Rennes (France), for assistance.